This study explores the effects of amount and source of dietary protein on bone turnover in pre- and post-menopausal women. To date, we have studied 16 premenopausal women as they consumed low, medium and high levels of dietary protein and have shown a marked effect on mineral metabolism and bone turnover. Specifically, on the low protien diet we observed secondary hyperparathyroidism with reduced intestional calcium absorption as assessed by stable calcium isotopic studies. In addition, the low protein diet was associated with evidence for slightly diminished bone turnover. On the high protein diet, although calcium absorption was normal, there was evidence for increased bone resorption. These studies are currently being extended to post-menopausal women and to men.